mei: nfc: fix deadlock on shutdown/suspend path

In function mei_nfc_host_exit mei_cl_remove_device cannot be called
under the device mutex as device removing flow invokes the device driver
remove handler that calls in turn to mei_cl_disable_device which
naturally acquires the device mutex.

Also remove mei_cl_bus_remove_devices which has the same issue, but is
never executed as currently the only device on the mei client bus is NFC
and a new device cannot be easily added till the bus revamp is
completed.

This fixes regression caused by commit be9b720a0ccb ("mei_phy: move all
nfc logic from mei driver to nfc")

Prior to this change the nfc driver remove handler called to no-op
disable function while actual nfc device was disabled directly from the
mei driver.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/mei/bus.c

@@ -552,22 +552,6 @@ void mei_cl_bus_rx_event(struct mei_cl *cl)
 	schedule_work(&device->event_work);
 }
 
-void mei_cl_bus_remove_devices(struct mei_device *dev)
-{
-	struct mei_cl *cl, *next;
-
-	mutex_lock(&dev->device_lock);
-	list_for_each_entry_safe(cl, next, &dev->device_list, device_link) {
-		if (cl->device)
-			mei_cl_remove_device(cl->device);
-
-		list_del(&cl->device_link);
-		mei_cl_unlink(cl);
-		kfree(cl);
-	}
-	mutex_unlock(&dev->device_lock);
-}
-
 int __init mei_cl_bus_init(void)
 {
 	return bus_register(&mei_cl_bus_type);

drivers/misc/mei/init.c

@@ -333,8 +333,6 @@ void mei_stop(struct mei_device *dev)
 
 	mei_nfc_host_exit(dev);
 
-	mei_cl_bus_remove_devices(dev);
-
 	mutex_lock(&dev->device_lock);
 
 	mei_wd_stop(dev);

drivers/misc/mei/nfc.c

@@ -402,11 +402,12 @@ void mei_nfc_host_exit(struct mei_device *dev)
 
 	cldev->priv_data = NULL;
 
-	mutex_lock(&dev->device_lock);
 	/* Need to remove the device here
 	 * since mei_nfc_free will unlink the clients
 	 */
 	mei_cl_remove_device(cldev);
+
+	mutex_lock(&dev->device_lock);
 	mei_nfc_free(ndev);
 	mutex_unlock(&dev->device_lock);
 }